Technical grade ammonium chloride appears in the nitrogen fertilizer category for one reason: insoluble matter. Agricultural grade is entirely satisfactory when broadcast on soil, where a fraction of a percent of insolubles is irrelevant. It is not satisfactory in a drip line, a fertigation tank or a foliar spray, where the same insolubles accumulate at emitters and filters. This page covers the grade in soluble fertilizer applications; its industrial uses are on the technical grade page in the chemical products section.
Substance identity
| Chemical name | Ammonium chloride |
| Synonyms | Sal ammoniac, ammonium muriate |
| Formula | NH₄Cl |
| CAS | 12125-02-9 |
| PubChem CID | 25517 |
| Molar mass | 53.49 g/mol |
| Appearance | White crystalline powder or granules; technical grade should be white without off-white cast |
Specification
| Parameter | Value | Basis |
|---|---|---|
| NH₄Cl content, dry basis | ≥ 99.5 % | Typical commercial range |
| Nitrogen (N) | Approximately 26.0 % at 99.5 % purity | Calculated from 26.2 % theoretical |
| Moisture | ≤ 0.3–0.5 % | Typical commercial range |
| Water-insoluble matter | ≤ 0.02–0.05 % | Typical commercial range — the decisive parameter for this application |
| Sulfate (SO₄) | ≤ 0.02–0.05 % | Typical commercial range |
| Iron (Fe) | ≤ 5–10 mg/kg | Typical commercial range |
| Heavy metals, as Pb | ≤ 5–10 mg/kg | Typical commercial range |
| pH, 5 % solution at 25 °C | 4.5–6.0 | Typical range |
Properties
Solubility approximately 29 g per 100 g water at 0 °C, 37 g at 20 °C, 77 g at 100 °C. The steep temperature dependence has a direct field consequence: a stock solution made at midday concentration can precipitate overnight when the tank cools. Make up solutions at, or below, the concentration that stays dissolved at the lowest expected temperature, not at the highest.
Dissolution is endothermic at about +14.8 kJ/mol, so a large charge dissolved quickly cools the batch, which lowers solubility further and slows the remaining dissolution — add gradually and agitate. Solutions are acidic at pH 4.5–6.0 for 5 %, and this acidity is chemically useful in hard water, where it counteracts the tendency of alkaline water to precipitate calcium and magnesium salts in irrigation lines.
Applications
Fertigation and soluble fertilizer blends, where the nitrogen must go into solution completely and stay there. Chloride tolerance of the crop governs suitability exactly as it does for solid application — this is the same salt, and drip application does not make chloride disappear. In liquid blends, verify compatibility with the other components before mixing at scale: the safe test is a jar test at the intended concentrations, temperatures and water quality, held for the intended storage period, rather than a reasoned expectation.
The higher nitrogen content that follows from higher purity — about 26.0 % against 25.0–25.4 % — is a secondary benefit and rarely the reason for choosing this grade.
Handling and storage
Dry, sealed storage. Once in solution, chloride at fertigation concentrations is corrosive to mild steel, galvanised steel, copper alloys and aluminium, and raises pitting risk on austenitic stainless steel. Use plastic, GRP or lined tanks and fittings. Do not combine with alkaline stock solutions — the pH rise liberates ammonia and loses nitrogen. Flush lines after use rather than leaving solution standing.
Notes
Water quality matters as much as fertilizer quality. A high-purity salt dissolved in hard or high-bicarbonate water can still deposit scale at emitters, because the precipitate comes from the water and not from the fertilizer. Test the water before designing the programme.